Reactions of olefinic molecules in the presence of metal-containing catalysts to produce other olefinic molecules are known in the art as "disproportionation" reactions. The olefin disproportionation reaction can be visualized as the breaking of two existing double bonds between the first and second carbon atoms, and between the third and fourth carbon atoms, respectively, and the formation of two new double bonds, such as between the first and third carbon atoms and the second and fourth carbon atoms, respectively. A typical olefin disproportionation process is illustrated by U.S. Pat. No. 3,261,879, issued Jul. 19, 1966, to Banks, wherein two similar non-symmetrical molecules of an olefin react in the presence of certain catalysts to produce one olefin of a higher carbon number and one olefin of a lower carbon number. For example, propylene disproportionates by the process of U.S. Pat. No. 3,261,879 to produce ethylene and butylenes.
A variation of this disproportionation process, which might be termed "reverse disproportionation" is illustrated by the Netherlands Patent No. 6514985 of British Petroleum Company, Limited, published May 20, 1966, wherein, in one modification, molecules of two dissimilar olefins are reacted to form two molecules of a single olefin product, e.g.. ethylene and 2-butene react to form propylene.
Another variation of this process, being conveniently termed "ring opening disproportionation" to distinguish it from other variations, is disclosed by Netherlands Patent Application No. 6702703 of Phillips Petroleum Company, published Aug. 24, 1967, wherein a cyclic olefin and an acyclic olefin react to form a single product molecule. For example, ethylene reacts with cyclopentene by "ring opening disproportionation" to produce 1,6-heptadiene.
As used in this application, "disproportionation process" is meant to include all variations of disproportionations.
A variety of catalysts have been employed for conducting disproportionation reactions, such as those disclosed in U.S. Pat. No. 3,340,322, issued Sep. 5, 1967; U.S. Pat. No. 3,637,892, issued Jan. 25, 1972; U.S. Pat. No. 3,760,026, issued Sep. 18, 1973; U.S. Pat. No. 3,792,108, issued Feb. 12, 1974; U.S. Pat. No. 3,872,180, issued Mar. 18, 1975; and British Patent Specification No. 1,128,091, published Mar. 16, 1966. Among the catalysts that have been developed for disproportionation include inorganic refractory materials containing molybdenum and/or tungsten oxide.
Several patents disclose the use of promoter to enhance the disproportionation catalyst activity. Elemental metal promoters selected from the group consisting of barium, magnesium, tungsten, silicon, antimony, zinc, manganese and tin are disclosed in U.S. Pat. No. 4,568,788, issued Feb. 4, 1986, U.S. Pat. No. 4,522,936, issued Jun. 11, 1985, U.S. Pat. No. 4,524,235, issued Jun. 18, 1985 and U.S. Pat. No. 4,629,719, issued Dec. 16, 1986. In addition. organometallic compounds, such as aluminum and tin alkyls to promote solid catalysts including molybdenum and rhenium oxide for the disproportionation are disclosed in U.S. Pat. No. 4,454,368, issued Jun. 12, 1984 and U.S. Pat. No. 3,829,523, issued Aug. 13, 1974.
It is an object of this invention to provide a catalyst system with novel promoters for olefin disproportionation at high activity.
The present invention is therefore directed to a method of improving the activity of a disproportionation catalyst for converting olefins into olefins having different numbers of carbon atoms than the feed olefinic hydrocarbons.